<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<script>
        window.onload=function () {
            let input=document.getElementById("input");
            alert(input)
        }
            function selectChange() {
            alert("选项被改变了")
            }
</script>
<body>
<input type="text" id="input">
<select name="" id="" onchange="selectChange()">
    <option value="">湖南</option>
    <option value="">湖北</option>
</select>


</body>
</html>